The use of esters of phosphoric acid and their salts, such as, for example, the alkali metal, ammonium, and alkanolamine salts, as cleansers, emulsifiers, corrosion inhibitors, lubricants, thickening agents, primers, fillers, and binders is well known in the art. U.S. Pat. Nos. 4,153,649; 4,212,675; 4,278,129; 4,331,583; 4,350,645; and 4,367,247 describe various phosphoric acids, their preparation and uses. Certain commercial cleansers now on the market, e.g. GAFAC RA-600 (GAF Corporation) and MONOFAX 831 (Mona Industries) are phosphoric acid esters.
The phosphoric acid esters now being marketed include both long and short chain alkyl esters, alkyl-poly(alkoxy)-alkyl esters, alkyl-phenyl-poly(alkoxy)-alkyl esters, aryl esters, aralkyl esters, and hetero esters. These esters may be monoesters of the formula ##STR3## or diesters of the formula ##STR4## where A.sub.1 and A.sub.2 are the residues of the alcohol moiety and may be the same or different.
These esters possess one or more undesirable properties which detrimentally affect their utility as cleansing agents. For example, the diesters are poor detergents and have low water solubility. Many monoesters with a relatively high percentage of diesters display increased surface tension in aqueous solution as the pH increases--a property which reduces their cleansing effectiveness. Some acid esters have poor compatibility with their alkali metal salts which limits their use when both the free acid ester and salts thereof are present.
Many foam cleansers now in use are not particularly stable and tend to precipitate on standing unless large amounts of hydrotropes are added to stabilize the system. While hydrotropes do stabilize the system, they add little or nothing to the cleansing properties and are essentially dead-weight as far as providing better cleaning.